Capillary zone electrophoresis as a tool to monitor the hydrolytic degradation of a water-soluble poly(esteramide)

Abstract

The potential of CZE for monitoring the hydrolytic degradation of a water-soluble poly(esteramide), namely a polycondensate of 1-amino-1-deoxy-2,3,4-tri- O-methyl-5- O-[(pentachlorophenoxy)succinyl]- d-xylitol hydrochloride (PXS) was tested. Capillary zone electrophoresis (CZE) with a fused-silica capillary filled with phosphate buffer was used as such or after preliminary rinse with a polycation solution, according to the polycation dynamic adsorption method. Combination of these processes allowed us to show that PXS chains were cleaved at the level of ester bonds under mild conditions (25 °C and pH ranging from 5.5 to 8.0), amide bonds being stable. It is shown that the rate of ester cleavage is pH-dependent; the higher the pH the faster the cleavage. Degradation generates two types of oligomers, the first one with a negatively charged carboxylate group at one chain-end, and the second one with a terminal imide ring.